Insulation board



loo-s Patented Aug. 21, 1951 CRQSS REFEREHCE UNITED STATES PATENT OFFICEINSULATION BOARD Harvey R. Anderson, Eureka, Pa., assignor to Keasbeyand Mattison Company, Ambler, Pa., a corporation of Pennsylvania NoDrawing. Application June 8, 1949,

Serial No. 97,907 7 8 Claims. (01. 10s-W This application is acontinuation-in-part of my copending application for U. S. Patent,Serial No. 690,587, filed August 14, 1946, now abandoned.

This invention relates to heat insulating composition board, and aprincipal object of the invention is to provide a board of this classhaving generally improved physical characteristics.

More specifically, an object of the invention is to provide a heatinsulating board of homogeneous structure susceptible of manufacture inthe form of large sheets and exhibiting a relatively high strength for amaterial of the class exhibiting pronounced heat insulatingcharacteristics.

Another object is to provide an improved insulation board suitable foruse as bulkheads, fire barriers, heat insulating walls and the like, andcomposed essentially of chrysotil e asbestos, silivceous iliihnira'ffilii'e PM Heretofore in the manufacture of boards of this class,the use of chrysotile asbestos fibres have been avoided for the reasonthat they failed to afiiordmard of the required density, strength andthermal characteristics, an i has been generally accepted that the bestresults were obtainable by use of asbestos fibres of the amosite type.Thus in U. S. Patent Nos. 2,326,516 and 2,326,517 it is specificallystated that to obtain a thermal conductivity of less than one and aminimum modulus of rupture of 1500 pounds per square inch in a heatinsulating material of this -nature having a density of the order of 40pounds per cubic foot, asbestos fibres of the amphibole variety havingwater of crystallization not hlgh er than per centsfiouldbe used.mchrysotile islclstos'fibrs'have in the neighborhood of 14. per centWater, either as mm of or gstalligatignpr of both, and were, therefore,considered unsuitable for production of insulation board in accordancewith the principles set forth in the aforesaid patents. .I havediscovered, however, that so ti besto s possess the physicalcharacteristics required for the formation of a thermal insulating sheetin which a thermal conductivity of less than one and a transversestrength in excess of 1500 pounds per square inch may be secured with aboard density of 40 pounds per cubic foot or less. In accordance with myinvention, it has been found possible to obtain transverse strengths inexcess of 3,000 pounds per square inch at a density of substantially 40pounds per cubic foot, together with a thermal conductivity of less thanone at a mean temperature of 100 degrees Fahrenheit expressed as B. t.u.s per inch per hour per square foot per degree Fahrenheit.

I am aware of the fact that many chrysotile asbestos fibres do not havethe characteristics required to produce a board of the abovecharacteristics. These unsuitable fibres have a tendency to form in awater slurry a mass having great physical aflinity for water to anextent which interferes with removal of excess water in the formation ofthe sheet. This results in a sheet of high density in the area adjoiningthe face from which the water is removed and a very low density at theface to which pressure was applied. Thus the structure does not possessa uniform porosity or hardness, nor pores of a size conducive to a lowheat transmission value. Further, such sheets require excessive surfacepreparation, with resultant material losses, as by sanding, to obtain afinish suitable for commercial application and even so, do not possesssufficient hardness to alleviate excessive damage in normal commercialuse. Chrysotile fibres of the nature I have found suitable for a sheetof this type do not present such difliculty and, unexpectedly, produce asheet with a low heat transmission and exceptionally high transversestrength for the aforesaid low density. The sheet may be made very closeto the desired finished thickness and requires a minimum of sanding toprovide a smooth and hard surface suitable for painting or otherdecorative finishing. The surface is of sufficient hardness to preventscaling of applied decorative finish when subjected to the usualabrasive and impact loads in commercial use. Further, the sheetwithstands processing procedures without the usual damage and resultantrejection of imperfect sheets common to a soft sheet. A board producedin accordance with my invention shows a materially improved strength ascompared with the prior boards produced from amositefibre.

Chr sotile fibre suitable for use in the manufacture of the improvedsfiee't He'rein described may be differentiated from unsuitablechrysotile mg by first establishing e c arac r o fibre from a specificsource and then determining the grade from that source which may beused. This may be accomplished by means of the Quebec Standard" AsbestosTesting Machine in conjunction with a test of the wet volume of thefibre, milled to the extent giving the greatest bulk possible with thatfibre.

To determine the suitability of a chrysotile fibre from a specificsource, the fibre for this determination shall have a Quebec StandardAsbestos Testing Machine value not hi her than 2-8-4-2. If this fibre,after milling to the optimum state of bulk, has a wet volume value of atleast 40 cubic inches per pound of fibre, the fibre from that sourcewill possess the desired characteristics. The grade of fibre from thatsource having a wet volume value of 40 cubic inches per pound of fibreor greater will permit the manufacture of the type of sheet hereindescribed.

The Quebec Standard Asbestos Testing Machine and its use is familiar toall in the asbestos industry and is the accepted standard for gradingasbestos.

The wet volumes of the asbestos fibres are determined by means of adensitometer which measures the thickness of a wet filter cake ofconstant diameter which then permits the expression of the wet volumevalues in cubic inches. The apparatus consists of a piston of 1.75inches in diameter fitted within a cylinder. The travel of the piston ismeasured to a thousandth of an inch by means of a dial gauge. One end ofthe cylinder has a filtering member of No. 5 Whatman filter papersupported by a perforated filtering plate attached to the cylinder,which allows the escape of liquid but retains any material in solidform. The piston is moved by air pressure of magnitude sufficient toexert 25 pounds per square inch on the sample. In use, the air pressureis applied to the piston and thus to the sample. The pressure is appliedfor a period of time of suflicient duration to allow the travel of thepiston to cease. The slurried sample, three grams of fibre suspended in50 milliliters of water, is thus pressed against the filtering member toform a filter cake. Since the diameter is a fixed value, the thicknessmeasurement permits the calculation of the wet volume value of thefilter cake in cubic inches.

According to the invention, the board may be formed from a water slurryof suitable chrysotile fibres as herein specified, fine silica, andhydrated me by qompressing and,removing excess water mold having afilteriyg'scree'rii 'The'formed 'Boaidftb 'a'hardf'sti'ohg, and.relatively flexible structure by subjecting it to elevated Lempergturesand pressures by means of steam. In carrying out thisprocss, it ispreferaBle to open the chrysotile asbestos fibres to a great degree bypassage through a fiberizing mill. This fibre may then be mixed withfine silica and hydrated lime by conventional means.

If preferred, the fine silica and hydrated lime may be fed through themill togetheT'wdth the asbestos fibr e so as to obtain a blending of thedry ingredients simultaneously v'v'i't'hi the gpening of the fibres.rm'fy airxea*"rziatefia1tiics prepared'in the proper proportion aremixed with m to a sl ng; by conventional means. I prefer a quan ityofwater in the neighborhood 1200 per cent of me o gyvergfit r me scirdingredients in the mixture. This aurryflirprcper ount to afford thedesired density in the finished sheet, is then pressed to a solid blankform in a mold having its lower surface in the form of a screen orperforated sheet material to permit excess water to be substantiallyremoved by application of pressure. Sheets in thickness of about inch to1 inches may readily be produced in this manner. The formed sheet isthen removed from the mold, placed on a fiat pallet and allowed to agefrom 2 to days at atmospheric conditions before the final curing atelevated temperature and pressure is effected as by autoclaving.

4 I have found that if sheets are allowed to age from 2 to 5 days beforeautoclaving. the'r'e'fi? very little tendency for t'fi'' 'sheets toswell or check along the edges, and that the sheets may 5 be autoclavedwithout the use of confining weights or clamps. Portland cement may beused together with the lmskeletonized binder prior to and duringautoclaving. fie sheet is preferablygutoglaved atfrom iZjl I50unasrnergs ua a; c .s eemrr u may be piled 'iifa' "solid 'pneforautoclaving or may be spaced at intervals to facilitate the entranceof steam into the sheets.

The sheets thus autoclaved are dri sub- 5 stantially bone dry conditionin a suitable drier at a temperature above the boiling point of water,for instance, at about 250 degrees Fahrenheit. I thus obtain a sheetwhich is hard, has considerable fiexibility, is light in weight, andvery strong. The sheet, although having relatively fiat surfaces, may befurther finished by sanding or 'by other means as desired.

I havefound that it is possible to use 35 to 65 parts by weight of thespecified chryspjilaeasr bestos to 100 parts of the finished dry sheet,de-

pending on the physical characteristics desired. To obtain maximumstrength and good flexibility for a sheet of this nature, I prefer touse 50 per cent of the chrysotile begt os fib lle, as herein specified,to 100 parts of the finished dry sheet.

For example, a sheet made as heretofore described and composed of 50parts of the specified chrysotile asbestos fib re, 25 parts comminutedsiliclffafidaaparts hydrated Jime pxhibited a modiil iis of rupture of3310 pounds per square inch at a density of 41.4 pounds per cubic footwith a thermal conductivity (measured in B. t. u.'s per inch per hourper square foot per degree Fahrenheit) of 0.76.

It is preferable to have the silica slightly in excess of stoichiometricproport ons with the lime in order that the lime will be substantiallycom pletely reacted.

1ltl'i6figh"p'roducing a less desirable sheet, I have found the use ofminor amounts of chrysotile asbestos fibres not meeting the re uiremenfiof the chrysotile fibre Herein specifieagjasbesfis of the amphibolevariet or small amounts of pulped cellulose along with chrysotileasbestos fibres aFhf'n'i s ecified may be permissible.

Portland cement an oxide of any of the alkaline saith metals may be usedas a substitzfie for lime in the 5m der, although lime is preferred, andwhen Portland cement is thus used, the ratio of cement to siliciousmaterial is, preferably, about 2 to 1. When oxides of alkaline earthmetals other than lime are used and reaction is too slow, an acceleratorsuch as sodium carbonate may be used to speed the reaction. As the sili-00 ceous material, diatomaceous earth is preferred.

It will be understood that the details given are for the purpose ofillustration and not limitation or restriction, and that variationswithin the spirit of the invention are intended to be included 55 in thescope of the appended claims.

I claim:

1. As a new article of manufacture, a iight weight, hardand strongheat-insulating sheet material composed essentially of chrysotileasbestos fibres, whose characteristics are such that when gradingnothigher than 2-8-4-2 as determined on the Quebec Standard AsbestosTesting Machine, have a minimum wet volume value of 40 cubic inches perpound of fibre, and a hydraulic binder selected from the groupconsisting of the product resulting from the reaction in admixture withmoisture of hydrated lime and finely divided silica substantially instoichiometric proportions, the product resulting from the reaction inadmixture with moisture of Portland cement and finely divided silica,substantially in the proportions of two parts of Portland cement to onepart of silica, and mixtures thereof, said fibres constituting from 35per cent to 65 per cent of the dry weight of the finished material, andsaid material having a density of less than 45 pounds per cubic foot, amodulus of rupture substantially in excess of 1200 pounds per squareinch, and a thermal conductivity of less than one when measured at amean temperature of 100 degrees Fahrenheit.

2. A heat-insulating sheet material in accordance with claim 1 whereinthe elements of the said binder have been reacted substantially tocompleteness under the influence of steam.

3. A heat-insulating sheet material in accordance with claim 1 whereinthe hydraulic binder consists of the product resulting from the reactionin admixture with moisture of hydrated lime and finely divided silicasubstantially in stoichiometric proportions.

4. A heat-insulating sheet material in accordance with claim 3 whereinthe elements of said hydraulic binder binder have been reactedsubstantially to completeness under the influence of steam.

5. A heat-insulating sheet material in accordance with claim 1 whereinthe hydraulic binder consists of the product resulting from the reactionin admixture with moisture of Portland cement and finely divided silicain substantially the proportions of two parts of Portland cement to onepart of finely divided silica.

6. A heat-insulating sheet material in accordance with claim 5 whereinthe elements of said hydraulic binder have been reacted substantially tocompleteness under the influence of steam.

7. A heat-insulating sheet material in accordance with claim 1 whereinthe reactants in said hydraulic binder include both hydrated lime andPortland cement.

8. A heat-insulating sheet material in accordance with claim 7 whereinthe elements of said hydraulic binder have been reacted substantially tocompleteness under the influence of steam.

HARVEY R. ANDERSON.

REFERENCES CITED UNITED STATES PATENTS Name Date Smith June 3, 1947Number EXAMINEF

1. AS A NEW ARTICLE OF MANUFACTURE, A LIGHT WEIGHT, HARD AND STRONGHEAT-INSULATING SHEET MATERIAL COMPOSED ESSENTIALLY OF CHRYSOTILEASBESTOS FIBRES, WHOSE CHARACTERISTICS ARE SUCH THAT WHEN GRADING NOTHIGHER THAN 2-8-4-2 AS DETERMINED ON THE QUEBEC STANDARD ASBESTOSTESTING MACHINE, HAVE A MINIMUM WET VOLUME VALUE OF 40 CUBIC INCHES PERPOUND OF FIBRE, AND A HYDRAULIC BINDER SELECTED FROM THE GROUPCONSISTING OF THE PRODUCT RESULTING FROM THE RACTION IN ADMIXTURE WITHMOISTURE OF HYDRATED LIME AND FINELY DIVIDED SILICA SUBSTANTIALLY INSTOICHIOMETRIC PROPORTIONS, THE PRODUCT RESULTING FROM THE REACTION TIONIN ADMIXTURE WITH MOISTURE OF PORTLAND CEMENT AND FINELY DIVIDED SILICA,SUBSTANTIALLY IN THE PROPORTIONS OF TWO PARTS OF PORTLAND CEMENT TO ONEPART OF SILICA, AND MIXTURE THEREOF, SAID FIBRES CONSTITUTING FROM 35PER CENT TO 65 PER CENT OF THE DRY WEIGHT OF THE FINISHED MATERIAL, ANDSAID MATERIAL HAVING A DENSITY OF LESS THAN 45 POUNDS PER CUBIC FOOT, AMODULUS OF RUPTURE SUBSTANTIALLY IN EXCESS OF 1200 POUNDS PER SQUAREINCH, AND THERMA, CONDUCTIVITY OF LESS THAN ONE WHEN MEASURED AT A MEANTEMPERATURE OF 100 DEGREES FAHRENHEIT.